Background/aim Studies on the association between air pollution and metabolic control in children and adolescents with type 1 diabetes are rare. We examined the relationship between particulate matter with an aerodynamic diameter <10 µm (PM10), nitrogen dioxide (NO2) and accumulated ozone exposure (O3-AOT) and HbA1c and daily insulin dose (IU/kg body weight) in children and adolescents with type 1 diabetes.

Methods We investigated 32 879 type 1 diabetes patients<21 years documented between 2009 and 2014 in 340 German centres of the diabetes prospective follow-up registry (DPV). Long-term air pollution exposure (annual and quinquennial means) was assigned to 5-digit postcode areas of residency. Cross-sectional multivariable regression analysis was used to examine the association between air pollution and metabolic control. Models were adjusted for sex, age, diabetes duration, migration background, year of treatment, type of insulin treatment and Nielsen area to account for regional differences.

Results After comprehensive adjustment, HbA1c was significantly lower with higher O3-AOT-quartiles (O3-AOT-Q4: 7.89% [95%-confidence interval: 7.85; 7.93], O3-AOT-Q1: 8.20% [8.15; 8.24]). The inverse association between O3-AOT and HbA1c persisted after additional adjustment for degree of urbanisation or additional adjustment for PM10. Moreover, the inverse association remained stable in further sensitivity analyses. No significant associations between HbA1c and PM10 or NO2 were found. No association was observed between any of the three air pollutants and insulin dose.

Conclusion The inverse association between O3-AOT and HbA1c could not be explained by regional differences in diabetes treatment or other differences between urban and rural areas. Further studies on the association between air pollution and metabolic control in children and adolescents with type 1 diabetes are needed to confirm our observed association and to elucidate underlying mechanisms.